The invention relates generally to a method and apparatus for charging a propulsion battery of an electric vehicle. More specifically, the invention is directed to a method and apparatus for positioning a primary core-coil device of a inductive type battery charging system with respect to a secondary core-coil device of the same system and also to an apparatus for practicing the method.
A battery charging system plays a key role for utilization of electric vehicles and ease of handling the charging system helps to make the electric vehicle acceptable to and popular among prospective users. Therefore, a battery charging system easy to use is strongly demanded by the electric vehicle market.
Battery charging systems designed to facilitate the positioning of a primary core-coil device on a vehicle with respect to a ground secondary core-coil device have been disclosed heretofore by various prior art publications such as laid-open publications of Japanese unexamined patent applications Nos. 63-87136 and 3-155338 and laid-open publication of Japanese unexamined utility model application No. 1-79343.
In the charging system disclosed by the first publication No. 63-87136, an electric vehicle is driven to a predetermined position defined by wheel stops located in a garage so as to position a secondary core-coil device carried by the vehicle in confronting relation to a primary core-coil device of a battery charging apparatus installed on the garage floor. The correct position where the vehicle should be stopped for the charging operation is detected by a sensor and the charging apparatus is initiated automatically in response to a signal generated by the sensor. Thus, the vehicle driver can be freed from troubling to connect the primary core-coil device of the charging apparatus with the secondary core-coil device on the vehicle.
According to the charging apparatus disclosed by the publication No. 3-155338, the vehicle is driven carefully so that a secondary core-coil device on the vehicle is brought in abutment with a primary core-coil device of the ground charging apparatus. When such abutment is detected by a sensor, the charging apparatus is operated to flow electric current in the primary coil to initiate battery charging. With this apparatus, the vehicle driver does not have to manually connect the primary and secondary inductive devices.
According to the publication No. 1-79343, the vehicle is driven by the driver to a position where a secondary core-coil device mounted on the bottom of the vehicle is brought into alignment with a primary core-coil device which is placed on the floor of a parking location in a garage. When the alignment is detected by a proximity switch, the ground charging apparatus is operated to start the battery charging operation.
With any of the above-described charging apparatuses, the range of permissible crosswise distances within which the vehicle should be parked for successful coupling of the inductive core-coil devices is too small and, therefore, it is required that the driver should manipulate the steering wheel laboriously while driving the vehicle to guide it precisely to its charging position where the secondary core-coil device is set in alignment with the primary core-coil device. As a matter of course, this driving for positioning of the inductive devices calls for driving skill of the driver and consumes a lot of time before the vehicle can be properly located with respect to the ground primary core-coil device.
Additionally, the above prior art apparatuses use a costly sensor and its associated equipment. Furthermore, the prior art systems have a problem in that the ground chargers are subjected to rain fall.